A method of calculating concentration of multi-gas which is composed of multiple gases components of which are already known using ultrasound has been disclosed. By generating ultrasound in a space which is filled with multi-gas and detecting reflected ultrasound and calculating time of flight (TOF) between sending and receiving ultrasound, concentration of respective gas of multi-gas can be determined.
However, in a conventional method concentration of respective gas of multi-gas is calculated through complicated calculation and there is a limitation that pressure of respective gas cannot be determined together. Further, although concentration of respective gas is influenced by pressure thereof, the conventional method calculates concentration without consideration of pressure, so it is difficult to calculate precise concentration.